隔热层和黑色吸收膜对海水制盐的影响

对采用气泡塑料隔热板和黑色吸收膜的太阳能制盐效果进行数值模拟分析，讨论了盐池在蒸发海水过程中的动态特性和卤水的深度、天气条件、风速等参数对制盐效率的影响。与传统制盐方法相比，土壤对制盐的影响变小，卤水向地表渗漏损失可以避免，蒸发效率可提高１０％。     

高温气流中双液滴蒸发过程实验研究

建立了液滴蒸发的实验系统,采用悬挂液滴法对高温气流中单、双液滴的蒸发特性进行研究.实验结果表明：双液滴实验时的液滴蒸发过程与单液滴蒸发过程类似;液滴间相互作用使液滴周围蒸汽的浓度增大,气液传质浓度差减小,液滴与周围环境的传质速度降低,使蒸发速率减小;在纯辐射环境中液滴间相互作用对蒸发过程的影响较强,在辐射对流环境中液滴间相互作用对蒸发过程的影响较弱.     

饱和含盐土壤高温蒸发速率及影响因素分析

通过对70℃下饱和含盐砂土的蒸发实验,获得土壤水分和盐分的分布特征,重点分析初始堆积高度、初始盐分浓度等因素对蒸发速率的影响。实验结果表明,含盐土壤高温蒸发先后经历预热阶段、表层盐分浓度升高至饱和阶段、盐盖快速生长阶段以及慢速蒸发阶段。与不含盐工况相比,高温含盐土壤蒸发过程出现明显的滞后现象。蒸发速率随初始堆积高度的增加而增大,但当超过毛细特征长度以后,蒸发速率又快速下降。初始盐分浓度对蒸发速率的影响较大,尤其是高浓度下表层盐盖的生长对水蒸气扩散的削弱作用占主导因素。Pe数越大,盐分越易在表层聚集和结晶,对蒸发速率的抑制作用越强,同时盐分在土壤内部分布的不均匀性越明显。     

光伏采卤的应用与实践

以西台吉乃尔盐湖地下卤水开采为例,介绍光伏采卤技术在该矿区的应用,分析卤水密度和粘度,探讨卤水开采和输卤工程设计,在常规光伏水泵控制技术基础上,光伏采卤系统中电气控制增加新的控制技术,创建并成功应用远程无线管理模式,具备完整的管理网络和管理软件,解决了光伏采卤系统日常运行管理和监视及数据记录。     

太阳辐照下湿份分层土壤中热湿传输的数值模拟

考虑温度对土壤湿分迁移的影响，建立描述存在干饱和层时的土壤热湿传递的数学模型，并就自然环境和恒定太阳辐照下两种情况进行数值模拟，获得不同环境条件下土壤中温度和湿分分布以及水分蒸发的动态特性，分析干饱和土壤层对土壤热湿迁移与水分蒸发以及温度对土壤湿分传输的影响。     

复合激光诱导荧光定量标定技术及其对喷雾特性研究的应用Ⅱ:喷射参数和环境参数对喷雾特性的定量分析

在改变喷射控制参数和环境参数的喷雾特性研究中,应用定量标定的试验结果深入开展了喷油压力、喷孔孔径、环境密度和环境温度对喷雾各个特性参数影响的研究。研究中发现,提高喷射压力能提高喷雾动能,加速液相喷雾的破碎、促进液相蒸发形成气相喷雾,提高贯穿速率,有利于喷雾的扩散和蒸发。小孔径的喷油嘴,虽然能够减少贯穿距离,但也同时减弱了喷雾和空气的混合空间范围;由于小孔径促进了喷雾的破碎和蒸发,气相喷雾分布均匀程度明显提高。环境密度高的条件下明显减小了喷雾的贯穿距离,这样虽然导致喷雾的扩散速率降低,但由于单位体积内气体量的大幅增加,加快了环境气体和喷雾之间的互相作用,更容易形成气相。环境温度对喷雾的蒸发速率起关键作用,液相喷雾贯穿距离随温度升高而减小,同时,气相最大当量比出现时间提前,这些说明环境温度升高,加速了环境气体和喷雾间的热交换,提高了喷雾的蒸发速率,最终促进气相快速形成。     

煤油单滴在相对静止和强迫对流环境下的蒸发规律

采用悬滴法对普通煤油和航空煤油两种液体燃料的单液滴在高温相对静止及强迫对流环境下的蒸发规律进行了实验研究,得到70余组有效实验数据.在本文条件下,对流可促进燃料液滴的蒸发,且对流速度越大,液滴蒸发速率越大;对流环境下普通煤油和航空煤油的蒸发规律存在差异,且同等条件下普通煤油的蒸发速率大于航空煤油.传统"折膜"理论蒸发模型与实验结果相比存在一定偏差;综合相对静止及对流环境的厚交换层蒸发规律研究,提出新的规律,并用实验结果检验.     

基于分子动力学的燃油液滴超临界蒸发特性

基于分子动力学模拟的方法,对氮气环境中单个烷烃液滴的蒸发过程进行了模拟研究,揭示了液滴在亚临界和超临界条件下液滴蒸发特性的显著差异．对正十二烷液滴在氮气环境内的蒸发过程进行分子动力学模拟,结果表明：在超临界温度和压力条件下,液滴的温度持续上升,能够超过燃油组分的临界温度;此时,液滴与周围气相区的密度差异近乎消失,气-液相交界变得难以辨别,明显不同于亚临界条件下典型的气-液两相蒸发特征;蒸发速率随环境温度的升高而增大．在较低的压力范围内,升高环境压力能够提升液滴蒸发速率,但当压力达到一个特定值后,随着环境压力的升高蒸发速率反而会降低,同时液滴转变为超临界蒸发状态所需的最小压力随环境温度的升高而降低．对于双组分混合液滴,在亚临界环境条件下,液滴内的轻质组分优先蒸发;而在超临界环境条件下,液滴内各个组分近乎保持同步蒸发,两个燃油组分共同主导液滴的完整蒸发过程．     

气化炉液池内单个高温气泡传热、传质的数值模拟

建立了气、液间传热传质数学模型,对单个热气泡在上升过程中与处于蒸发阶段的水之间的传热、传质规律进行了数值研究,获得了气泡半径、气泡温度、水蒸发速率以及蒸发量随时间的变化规律.研究表明:在水恒温蒸发阶段,由于传热传质的共同作用,气泡半径随着气泡的上升而变小,并逐渐趋于稳定;随着气、液间温度差的增大,气泡半径缩小得越快;在气泡与水开始接触时,水的蒸发速率及气泡内的水蒸汽增量最大;气泡温度在较短时间内急剧下降,并趋于稳定;随着气泡半径的缩小,气泡冷却速率提高;但随着接触时间的继续增加,对气体的冷却效果却无明显作用.     

湿压缩压气机及压缩系统性能的理论研究

详细介绍了在压缩系统中液滴蒸发速率的计算方法，通过这种方法得出了蒸发速率与压比、进口温度的关系；并且建立了理想和实际湿压缩的数学模型，在此基础上应用上述液滴蒸发速率的计算方法分别得出压缩终温、压缩功随喷水百分比及效率的变化关系。     

埋地热油管道预热启输过程外界气温及预热水温对土壤温度场的影响

在建立管道和土壤的非稳态传热模型的基础上,重点考虑土壤和管道的初始温度分布、外界大气温度的周期性变化、预热热水的温度变化,以及由于空气和热水温度变化引起的空气和热水热物理属性变化导致空气与土壤表面和热水与管道内壁之间对流换热系数的变化等诸多因素对土壤温度场建立过程的影响。     

Solar stills of inclined evaporating cloth

This article describes various solar stills with inclined evaporating surfaces. It also discusses theoretical studies of maximum annual solar energy absorbed in fastened inclined plane surfaces or in plane surfaces with adjustable slope, which have been performed at the University of Santa Maria, Valparaiso, Chile.

The University has studied the efficiency of solar stills with the evaporating cloth oriented to the sun in several ways. The relation of the cloth arrangement to solar radiation: transfer and absorption coefficient of the solar rays, thermal insulation, distances between evaporating surface and transparent cover, vapor leaks, enthalpy loss due to brine output, and wind were determined.

The influence of time on the various still material is discussed. Factors included are aging of the plastic covers (Oro T polyethylene, polystyrene, metacrylic polyester, etc.), alterations suffered by different types of evaporating cloths (yute, malva, canamo, etc.), insoluble salt deposition, and seals (organic and inorganic cement, neoprene, etc.).

The economics of solar stills with inclined evaporating cloths developed in Chile are considered. This includes annual costs of the materials, construction and maintenance costs of the stills, and specific production and cost of the distilled water in several locations.     

Interaction of the transfer processes in semitransparent liquid droplets

The study presents the mathematical model of unsteady heat transfer in evaporating semitransparent droplets of non-isothermal initial state and the numerical research method, evaluating selective radiation absorption and its influence on the interaction of transfer processes. The relation of the transfer processes inside droplets and in their surroundings and the necessity of thorough research of these processes are substantiated. When modeling the combined energy transfer in water droplets, the evaluation of thermoconvective stability in evaporating semitransparent liquid droplets is presented; the influence of the droplet initial state on its heating and evaporation process is investigated. The influence of heat transfer peculiarities on the change of the evaporating droplet state is indicated. Main parameters, which decide the peculiarities of the interaction of unsteady transfer processes in droplets and their surroundings, are discussed. The results of the numerical research are compared to the known results of the experimental studies of water droplet temperature and evaporation rate.     

Direct use of solar energy for water desalination

Solar energy utilization in three different types of solar desalination systems is considered. The overall efficiency of a typical basin type solar desalination plant is 30 per cent or lower. The major design factors affecting energy utilization are basin temperature, condensing surface temperature and ambient air temperature. Basic reflection and thermal radiation from the evaporating surface and transparent cover are the major sources of heat energy loss in a solar still. The efficiency of a solar desalination plant can be improved by controlling radiation from the plant basin and by the reuse of the latent heat of condensation.     

Effects of Non-Darcian and Inlet Conditions on the Forced Convection Along a Vertical Plate With Film Evaporation

The present study analyzes theoretically the non-Darcian effects and inlet conditions of forced convection flow with liquid film evaporation in a porous medium. The physical scheme includes a liquid–air streams combined system; the liquid film falls down along the plate and is exposed to a cocurrent forced moist air stream. The axial momentum, energy, and concentration equations for the air and water flows are developed based on the steady two-dimensional (2-D) laminar boundary layer model. The non-Darcian convective, boundary, and inertia effects are considered to describe the momentum characteristics of a porous medium. The paper clearly describes the temperature and mass concentration variations at the liquid–air interface and provides the heat and mass transfer distributions along the heated plate. Then, the paper further evaluates the non-Darcian effects and inlet conditions on the heat transfer and evaporating rate of liquid film evaporation. The numerical results show that latent heat transfer plays the dominant heat transfer role. Carrying out a parametric analysis indicates that higher air Reynolds number, higher wetted wall temperature, and lower moist air relative humidity will produce a better evaporating rate and heat transfer rate. In addition, a non-Darcy model should be adopted in the present study. The maximum error for predictions of heat and mass transfer performance will be 21% when the Darcy model is used.     

太阳辐射强度和温度对增强型冷却塔换热性能影响的研究

太阳能增强型自然通风冷却塔(SENDDCT)作为一种新型空气冷却系统,可利用太阳能提高自然通风冷却塔的效率。利用FLUENT软件建立太阳能增强型冷却塔的三维模型,研究太阳辐射强度和环境温度对其性能的影响;同时设计并搭建太阳能增强型冷却塔的实验系统,在实际天气条件下研究太阳辐射强度对其换热性能的影响。模拟结果表明太阳辐射强度一定时,通过换热器的空气流速以及换热率都会随着环境温度升高而降低。太阳辐射强度为500 W时,环境温度由10℃升到40℃,换热率由1.106 kW下降到0.281 kW。实验结果表明有辐射时冷却塔入口处的平均空气温度要比无辐射时的高5℃;实验期间无辐射时的平均换热率为0.682 kW,有辐射时的平均换热率为0.794 kW,即利用太阳能将平均换热率提高了0.112 kW。     

不同环境条件下土壤温度日变化的计算模拟

应用多孔介质中传热传质的数学模型，对夏天和冬天，环境风速分别为4m／s和1m／s以及环境相对湿度分别为35％和85％这3种情况下高为500mm，半径为250mm的圆柱土壤床中温度的日变化进行了比较。根据数值模拟的结果绘出土壤中不同深度处温度的日变化曲线表明：(1)土壤中各点的温度随气温和土壤表面获得的辐射能的周期性变化而呈周期性变化；(2)随着深度的增加，土壤温度受气温和太阳辐射的影内变小，温度变化的滞后效应越来越明显；(3)在夏天，一天的大部分时间土壤表层的温度高于深层的温度，冬天则恰恰相反；(4)风速对土壤表层的温度影内较大。风速越大，土壤温度降低得越多；(5)干燥气候下，由于土壤水分的蒸发制冷作用，一天中土壤各点的温度低于湿润气候下相应各点的温度，土壤表层尤为明显。     

基于能量流的塔式太阳能热发电吸热器动态建模

塔式太阳能热发电空气吸热器的最大热应力与其温度变化率成正比,吸热器出口空气温度的动态特性影响塔式光热系统的功率特性。结合热电比拟理论,采用对流换热系数和Rosseland辐射传递方程描述传热过程,建立塔式太阳能热发电系统中碳化硅泡沫陶瓷吸热体的能量流模型。通过剖析空气吸热器工作过程的传热特性,得出平均能流密度、吸热体厚度、平均孔径对出口空气温度、吸热体温度的影响,为该类空气吸热器的设计提供了理论依据。     

高效换热管中R22传热特性的试验研究与分析

针对海水冷却的特点和要求,研究了Ｒ２２在高效换热管管内蒸发和管外冷凝的传热和压降特性,并就传热特性与相关文献报道进行了比较。实验结果表明,耐腐蚀铜合金高效换热管作为冷凝时,其传热性能比普通换热管要高出一倍左右。这些研究和分析对热泵空调换热器优化设计及海水高低温热源的应用具有重要意义。     

Axisymmetric natural convection-driven evaporation of water: Analysis and numerical solution

Coupled steady laminar heat and mass transfer from an evaporating circular pool of water into quiescent dry air is considered in the limit of large Rayleigh number (Ra). The resulting boundary-layer equations are reformulated in similarity-like variables that are necessary for numerical implementation; different variables are necessary, depending on whether the water is hotter than the ambient air, or vice versa. The governing partial differential equations are solved using a finite-element method and the dependences of the dimensionless Nusselt (Nu) and Sherwood (Sh) numbers on the water temperature and the ambient air temperature are determined.